Optical switches of various kinds for selectably switching incoming light from one optical fiber or light-conducting path to another are well known and used in many applications. In some cases, ganged operation of optical switches is required, when two or more optical beams, e.g. received from two or more input fibers, have to be simultaneously switched.
An example of such application is bypass switching in optical networks, when bi-directional optical traffic has to be quickly redirected to bypass an optical ring or a node. Typically, this redirecting is accomplished using a 2×2 bypass switch in each direction of optical traffic flow, as illustrated in FIG. 1, showing both normal and bypassed optical traffic flow. A ring network 6 shown comprises nodes 1, 2, 3 and 4, connected in a serial fashion. A 2×2 bypass switch 5 serves as an interface between the ring and node 3; it can route optical information in either of two ways. This is illustrated in FIG. 1 by showing one state of the 2×2 switch as block 5a and the other as block 5b with blocks 5a and 5b connected to node blocks 3a and 3b, respectively. It should be understood that a single node 3 and single bypass switch 5 are in fact employed. The normal optical traffic flow to and from the node 3 through the ring 6 corresponds to a cross-state of the bypass switch illustrated by the block 5a. If a node fails or is disconnected, the ring will fail unless continuity of the ring is maintained. The block 5b illustrates a second state of the bypass switch 5 in which the ring continuity is maintained. Upon failure or disconnection of node 3, the node is bypassed by optical loopback, which can be referred to as a bypass or a loopback state.
A compact and efficient 2×2 optical bypass switch is disclosed by the inventor of the present invention in U.S. Pat. No. 6,353,692, assigned to JDS Uniphase, the assignee of the instant application, which is incorporated herein by reference. Advantageously, the switch employs only one lens and is single-sided, i.e. has all the input and output optical fibers at one side thereof, which enables compact packaging.
To address the requirement for optical bypass switching in bidirectional links, two conventional 2×2 optical bypass switches, synchronized and possibly bundled together, are commonly used. For example, Young et al. in U.S. Pat. No. 6,920,277 issued Jul. 19, 2005 disclose an architecture and method of creating optical bypass of a terminal node using two bypass switches. In another example, Wang et al. in U.S. Pat. No. 6,813,241 issued Nov. 2, 2004 disclosed a network architecture for link protection in a bidirectional data traffic network with a dual switch configuration consisting of two 1×2 optical switches.
The aforementioned prior-art solution, wherein two individual optical switches are combined together, provides a dual optical switch, which, although performing its intended function, is roughly twice as bulky and costly as a single switch.
The object of this invention is to provide a compact single-sided optical multi-switch device, wherein individual switches of said device share at least some of the optical components for reducing the size and complexity of the device.
Another object of this invention is to provide a simple and compact dual 2×2 optical bypass switch comprising a smaller number of optical components than two separate 2×2 optical bypass switches.
Another object of this invention is to provide a simple and compact dual optical switch comprising a single lens and a single switching element.